Various reinforcement fibers and their use in a wide variety of applications are known in the art. For example, it is known to add reinforcement fibers to building materials, such as concrete, including Portland cement concrete, asphalt cement concrete and the like, to add strength, toughness, and durability, and to improve the integrity of the cement properties. In some applications, reinforcement fibers are added to concrete to reduce or prevent cracks. Typical reinforcement fibers include asbestos fibers, glass fibers, steel fibers, mineral fibers, natural fibers, synthetic fibers, such as polymer and aramid fibers, elastane fibers, and cellulose fibers. Some reinforcement fibers are better suited for particular applications than others. For example, asbestos fibers are known to provide effective reinforcement but, due to environmental and health concerns these fibers, are not extensively used. In addition, some fibers are relatively expensive and therefore, not practical for all applications.
Reinforcement fibers are incorporated into the building materials, such as Portland cement concrete and asphalt cement concrete, using a variety of conventional methods and techniques. For example, it is known to add reinforcement fibers to Portland cement concrete and asphalt cement concrete during the manufacturing process prior to field placement. For example, in a batch process wherein a mixing machine is used to produce concrete, reinforcement fibers are added to a mixing chamber having mixing blades, with other ingredients. A continuous process uses a drum mixer and the reinforcement fibers are added to the drum mixer. When asphalt cement concrete is produced, the reinforcement fibers are typically added to the mixer prior to the introduction of liquid asphalt. Further, the reinforcement fibers may be added to equipment other than the mixing chamber and the drum mixer. In general, the reinforcement fibers may be added to any associated machinery located either up-line or down-line from the mixing machine or the drum mixer provided that the machinery has the capability to provide sufficient mixing and dispersion of the reinforcement fibers in the asphalt composition.
The reinforcement fibers are added to a cement concrete composition either individually or in a bundle or in a container. Generally, it is advantageous for the reinforcement fibers to be added in a manner that is effective to reduce or minimize entanglement and clumping, and to improve or maximize distribution throughout the composition.
Further, reinforcement fibers can be added to a cement concrete composition in varying amounts. Typically, the amount added is such that desired properties of the reinforced concrete are achieved upon field placement.
There are disadvantages associated with the known methods for introducing reinforcement fibers into Portland and asphalt cement concrete compositions. For example, there is room for improvement in introducing reinforcement fibers, e.g., having a length of ½″ or greater, such that they are easily dispersed and uniformly distributed in the cement concrete composition, and provide improved strength, durability and toughness in the reinforced concrete upon its field placement.